Monochloroacetone is a chemical intermediate used in the preparation of thiabendazole. Thiabendazole is an antiparasitic agent useful for the treatment of parasitic infections in domestic animals and in humans and also an antifungal agent for use in agriculture for the prevention of fungal diseases in stored crops and grains, and also for the suppression of fungal growth in aqueous and nonaqueous systems such as paints. The chemical procedures used for the preparation of monochloroacetone are well known, see for example U.S. Pat. No. 2,116,893 to Meisel issued May 10, 1938, U.S. Pat. No. 2,235,562 to Rahrs issued Mar. 18, 1941, U.S. Pat. No. 2,234,484 to Morey issued May 27, 1941 and U.S. Pat. No. 3,397,240 to Kaufman et al. issued Aug. 13, 1968.
The current state of the art process for the preparation of monochloroacetone as described in the Kaufman et al. patent above involves the direct reaction of acetone and chlorine. The reaction is carried out in vapor phase and produces monochloroacetone in yields in excess of 90%. The reaction uses an acetone:chlorine ratio of about 10:1 thus the reaction effluent will contain monochloroacetone as well as unreacted acetone and hydrogen chloride a reaction by-product. In addition some polyhalogenated acetone may be present as well as the reaction product of hydrogen chloride and acetone-mesityl oxide. The reaction effluent is fractionated to recover the monochloroacetone in adequate purity for future use. However, fractionator effluent is quenched with water and this mixture of acetone, hydrogen chloride and water was extractively distilled yielding an acetone fraction unsuitable for recycling back into the reaction mixture and the hydrogen chloride fraction therefrom has quantities of acetone and other organic by-products to such an extent that the material was not usable for any other chemical reaction procedures. As a result, most of the reaction effluent had to be discarded owing to the presence of quantities of monochloroacetone, an extremely powerful lacrimator. The disposal of these materials presented considerable environmental problems and the extractive distillation apparatus required considerable energy input. In the instant process, all of the acetone containing small amounts of monochloroacetone and reaction by-products along with some hydrogen chloride is recycled back into the monochloroacetone reactor or into the fractionator. The hydrogen chloride which is recovered is substantially free of organic materials and may be compressed into liquid hydrogen chloride or quenched with water to form concentrated hydrocloric acid for use in other chemical procedures or for sale to those who can so use such acid.